Make @module-federation/runtime-tools optional

Currently, @module-federation/runtime-tools is a direct dependency of @rspack/core.

In Rspack 2.0 we can make it an optional peer dependency to reduce dependencies.

Context

Currently, Rspack's built-in @module-federation/runtime-tools is only used when using the MF 1.5 plugin and the implementation option is not set.

• If the application uses MF 2.0, only @module-federation/enhanced -> @module-federation/runtime-tools will be used:

devDependencies:
@module-federation/enhanced 0.14.0
└── @module-federation/runtime-tools 0.14.0
@rspack/core 1.2.8
└── @module-federation/runtime-tools 0.8.4  ---->  never used!

• If the application uses MF 1.0 or does not use MF, Rspack's built-in @module-federation/runtime-tools will never be used.

Benefit

By making @module-federation/runtime-tools optional, we can avoid installing unnecessary dependencies in the application and speed up the npm installation.

6 dependencies can be removed:

buitin:swc-loader

Enable verbatimModuleSyntax: true by default

Typescript import elision is a footgun for bundler which can eagerly remove module with sideEffect, and TypeScript introduce a new safe option to disable this behavior which should be enabled by default for builtin:swc-loader.

Ref:

• https://swc.rs/docs/migrating-from-tsc#verbatimmodulesyntax-true
• https://www.typescriptlang.org/tsconfig/#verbatimModuleSyntax

Drop Node 18 support

Node.js 18 and all earlier versions are End-Of-Life since April 30, 2025, see https://nodejs.org/en/blog/announcements/node-18-eol-support

I'm not sure whether we can drop Node 20 support.

Ref:

• https://nodejs.org/en/about/previous-releases

Remove config.stats.profile and config.profile support

Rspack recommend use tracing for debugging performance issue and consider remove stats.profile has config.profile support

Simplify target configuration

In Rspack 2.0, we can make Rspack's target option affect the default targets of SWC and LightningCSS (which can still be manually overridden), ensuring that users only need to configure target once, rather than setting target in multiple different places.

Ref:

• https://rspack.rs/config/target#target
• https://rspack.rs/guide/features/builtin-swc-loader#syntax-lowering
• https://rspack.rs/guide/features/builtin-lightningcss-loader#targets
• https://rspack.rs/plugins/rspack/lightning-css-minimizer-rspack-plugin#minimizeroptions

Before

export default defineConfig({
  target: ['web', 'es2022'],
  module: {
    rules: [
      {
        test: /\.js$/,
        use: {
          loader: 'builtin:swc-loader',
          options: {
            jsc: {
              target: 'es2022',
            },
          },
        },
      },
      {
        test: /\.css$/,
        use: [
          {
            loader: 'builtin:lightningcss-loader',
            options: {
              targets: 'Chrome >= 93', // -> es2022
            },
          },
        ],
      },
    ],
  },
  plugins: [
    new rspack.LightningCssMinimizerRspackPlugin({
      minimizerOptions: {
        targets: 'Chrome >= 93', // -> es2022
      },
    }),
  ],
});

After

export default defineConfig({
  target: ['web', 'es2022'],
  module: {
    rules: [
      {
        test: /\.js$/,
        use: { loader: 'builtin:swc-loader' },
      },
      {
        test: /\.css$/,
        use: [
          { loader: 'builtin:lightningcss-loader' },
        ],
      },
    ],
  },
  plugins: [new rspack.LightningCssMinimizerRspackPlugin()],
});

Default options of stats.toJson()

Currently, stats.toJson() has all: true enabled by default, which causes significant communication overhead between Rust and JS, affecting the performance of large applications.

In Rspack 2.0, we need to improve the default options of stats.toJson() to avoid this problem.

@SyMind cc

Consider ignoring aliased dynamic require

We're considering skipping aliased dynamic require by default, which would help reduce bundle size for libraries like moment.js and align with other bundlers' behavior, though whether this should be changed remains open for discussion.

var aliasRequire = require
aliasRequire('./locale' + name)

See filipsobol/bundle-size-benchmark#2 for more details.

Remove the output.charset configuration

See #11594 (comment)

Remove the built-in webpack-bundle-analyzer

In the early versions of @rspack/cli, we built-in the webpack-bundle-analyzer package for bundle size analysis. Considering that Rsdoctor now supports analyzing bundle size, we can remove this built-in functionality from @rspack/cli to reduce the install size.

Related:

• Bundle analysis
• Rsdoctor - Bundle analysis

Simplify and unify browserslist implementation

Simplify and unify browserslist implementation between targets、swc-loader(swcMinimizerRspackPlugin) and lightningcss-loader(LightningCssMinimizerRspackPlugin)
The current browserslist target configuration is too complex and different from (swc,lightningcss) loader and minimizer, we should consider unify and simplify it.

Remove rspackFuture

rspackFuture is only used for rspackFuture.bundlerInfo and most options are put in experiments, so it's unnecessary to keep rspackFuture option

Refactor module.unsafeCache

1. The behavior of module.unsafeCache in Rspack is inconsistent with that in Webpack.

2. Additionally, this configuration partially overlaps in functionality with watch.ignored.

We are considering renaming this configuration to a more appropriate term and redesigning its functionality to differentiate it from Webpack.

Related PR: #11898

Refactor RuntimeModule.constructorName

Currently, a constructorName property has been added to the JavaScript side of RuntimeModule to differentiate between various RuntimeModules. This approach is too hacky. We should attempt to leverage the constructor itself directly to achieve this functionality.

Deprecate or Remove this._module support

this._module is indeed a unsafe api for Rspack consider it will cause access and mut access of module from both JavaScript side and Rust side together and it's also a hacky API from webpack

Is Rspack 2.0 still compatible with webpack@5?

Remove WarnCaseSensitiveModulesPlugin

The WarnCaseSensitiveModulesPlugin had been deprecated and can been replaced by CaseSensitivePlugin in #12532. So we can just remove the WarnCaseSensitiveModulesPlugin in v2.0

Remove plugin.getHooks

The hooks of plugins like HtmlRsapckPlugin, RuntimePlugin and RsdoctorPlugin can be got by plugin.getCompilationHooks which is renamed from plugin.getHooks. So we can remove plugin.getHooks in v2.0

Remove draft option of LightningCSS

The draft had been deprecated and replaced with drafts. So we can remove draft in v2.0 and use drafts instead.

Remove deprecated output.library options

The deprecated library options on output that had been moved to output.library:

• output.libraryExport - replaced with output.library.export
• output.libraryTarget - replaced with output.library.type
• output.umdNamedDefine - replaced with output.library.umdNamedDefine
• output.auxiliaryComment - replaced with output.library.auxiliaryComment

Default global identifiers updated

The default values of some runtime global identifiers have been updated to better reflect the Rspack brand.

// Before (Rspack 1.x)
output.hotUpdateGlobal = `webpackHotUpdate${uniqueNameId}`;
output.chunkLoadingGlobal = `webpackChunk${uniqueNameId}`;

// Now (Rspack 2.0)
output.hotUpdateGlobal = `rspackHotUpdate${uniqueNameId}`;
output.chunkLoadingGlobal = `rspackChunk${uniqueNameId}`;

Enable experiments.async_web_assembly by default

Previously, asyncWebAssembly was only enabled by default when experiments.futureDefaults was set to true. We can enable it by default in v2.0 and just use it with type: 'webassembly/async'

Disable parser.javascript.requireAsExpression by default

When requireAsExpression is enabled, rspack emits a "Critical dependency" warning whenever require is used as an expression (e.g., var r = require;). By disabling it by default, we avoid these warnings in typical scenarios while still allowing users to opt-in if they need this behavior.

Use 'rspack' as default fallback value of output.trustedTypes.policyName

The policyName will use output.uniqueName first, and then fallback to rspack instead of webpack.

Move experiments.incremental to top-level

It's already stable and enabled since v1.4 so we move the config out of experiments

Change default value for devtool

• Changed development mode default from 'eval' to 'cheap-module-source-map'
• Changed production mode default from 'source-map' to false in the CLI

Change module.parser.javascript.exportsPresence default to 'error'

• change module.parser.javascript.exportsPresence default to 'error'
• remove module.parser.javascript.strictExportPresence, since it's already deprecated

Remove deprecated readResourceForScheme hook

Remove the NormalModule.getCompilationHooks(compilation).readResourceForScheme() hook because it was never implemented in Rspack and has been deprecated in webpack (https://github.com/webpack/webpack/blob/124ba79918269ecc6018915655c993327947ff12/lib/NormalModule.js#L289-L290).

ProgressPlugin API

Update ProgressPlugin handler arguments:

// before
new rspack.ProgressPlugin((percentage, message ...args) => {
  // args: string[]
});

// after
new rspack.ProgressPlugin((percentage, message, info) => {
  // info: { builtModules: number; moduleIdentifier?: string }
});

Resolve's roots defaults to empty array

// before
resolve: {
  roots: [ context ] 
}

// after
resolve: {
  roots: [ ] 
}